A facility for raising 6,000 to 8,000 athymic mice is being organized. It is planned to grow a large number of human tumors in these mice. Studies will be carried out on the growth pattern of the human tumors and their properties both in vivo as well as their growth requirements and characteristics in tissue culture. Efforts will be made to determine whether human tumors produce specific substances in defined media. The treatment of tumors in the athymic mice will be correlated to the chemotherapy being received by the patient from which the tumor had been excised initially.